Pre-assembled Fastener Assembly with Cold Expansion Mandrel
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Solution Overview
Problem
The existing fastener assembly installation process is time-consuming and inefficient due to the need for multiple mandrels of varying sizes for different openings, and the process of installing threaded inserts and nut plates requires tedious mandrel replacement and potential compressive residual stresses in structural workpieces.
Innovation Solution
A pre-assembled fastener assembly with a captured, cold-expansion mandrel and a floating nut member that allows for quick installation by radially expanding a retainer into the structural workpiece, eliminating the need for post-installation cap attachment and reducing material stress, while enabling efficient reuse of the mandrel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple mandrels of varying sizes are used for different openings, then the correct amount of radial expansion can be achieved for each opening size, but the installation process becomes time-consuming and inefficient due to frequent mandrel replacement
Solution Approach 1:
The patent employs a universal mandrel design that can accommodate multiple opening sizes through interchangeable sleeves or adjustable mechanisms. This single mandrel system replaces the need for multiple specialized mandrels, maintaining precise radial expansion for different opening diameters while eliminating time-consuming mandrel replacement operations. The universal mandrel achieves this through modular components that can be quickly swapped or adjusted to match different opening requirements.
2Ease of manufacture
If the cap is attached after the nut plate is installed into the opening, then the installation process can be completed, but the overall installation time is increased due to the additional post-installation step
Solution Approach 1:
The patent applies preliminary action by pre-attaching the cap to the nut plate assembly before installation into the opening. This pre-assembly approach allows the cap and nut plate to be installed as a single integrated unit, eliminating the separate post-installation cap attachment step. The cap is positioned and secured in advance, so that when the entire assembly is installed into the opening, the sealing and structural functions are simultaneously achieved, significantly reducing total installation time.
3Weight of moving object
If a lightweight nut plate design is implemented, then the overall weight is reduced, but the resistance to torque and axial push/pull-out may be compromised
Solution Approach 1:
The patent utilizes composite material construction for the nut plate, combining materials with different properties to achieve both lightweight design and high strength. The composite structure may include high-strength alloys, fiber-reinforced materials, or multi-layer constructions that provide superior torque resistance and axial load capacity while maintaining reduced weight. This composite approach allows the nut plate to meet strength requirements without the weight penalty of traditional solid metal constructions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables rapid, efficient installation of nut plates and threaded inserts with improved resistance to torque and fatigue, reduced material stress, and a lightweight design, enhancing installation speed and structural integrity.
Implementation Method 1
A pre-assembled fastener assembly with a captured, cold-expansion mandrel and a floating nut member that allows for quick installation by radially expanding a retainer into the structural workpiece
Implementation Method 2
The radial expansion of the collar into the opening may induce compressive residual stresses into the surrounding material of the structural workpiece. The compressive residual stresses may increase the fatigue performance of the structural workpiece in the vicinity of the opening.
Data Source
Figure 1
Figure 2A~2B
Figure 3~5
AI summary
This disclosure relates to a pre-assembled fastener assembly (10) having a retainer (14), a nut member (18), and a cold expansion mandrel (12) that is forcibly removable after the assembly is installed into an opening (20) of a structural workpiece (22) . The mandrel is captured between a portion (39) of a retainer and a portion (60) of a nut member. The forced removal of the mandrel expands the retainer into the opening, securing the fastener assembly therein. The assembly may also include a cap (16) coupled to the retainer to seal the opening in the structural workpiece. The nut member can be fixed or free-floating with respect to the retainer. In addition, the nut member can be threaded to receive a fastener. The mandrel is recyclable or disposable.